Loads connected to electrical circuits can be damaged if the loads draw more current than they are configured to tolerate. For example, inductive motor loads that draw too much current from a power source can suffer from overheating, which shortens the motor life and can potentially break down the insulation in the motor windings. Additionally three-phase inductive motor loads configured to receive power from a polyphase AC power source can be damaged if the power source suffers from a phase loss or phase imbalance. A phase loss occurs when one phase of the current delivered by the polyphase power source is disconnected. A phase loss fault can occur due to a blown fuse or a discontinuous power wire in series with the conductor carrying the phase. A phase imbalance fault occurs when one or more of the phases of the current drop below some characteristic fraction of their nominal values. A phase loss fault and a phase imbalance fault can damage the motor load by causing the motor windings to draw current unevenly and heat unevenly, which is inefficient and shortens the life of the motor and potentially overheats the insulation of the motor windings. Therefore, an electronic protection device is conventionally used to protect the motor.
The electronic protection device can be configured to automatically reset following tripping of the electronic protection device. Electronic protection devices incorporating selective automatic reset functionality conventionally include an external power source for powering a memory or a logic circuit to provide a reset function following the tripping. The external power source provides power to logical aspects or memory aspects within the electronic protection device for storing the type of fault condition determined by the controller after the trip mechanism is actuated. A conventional electronic protection device having selective automatic reset functionality can then determine whether to automatically reset following a trip event based on the contents of the separately powered memory. But, conventional electronic protection devices require an external power source to provide selective automatic reset functionality. Providing a separate power source undesirably adds cost and current consumption to conventional electronic protection devices, and requires additional electronic components and circuitry.